Math Problem Statement

Write the absolute value function f(x) = |3x + 4| as a piecewise-defined function with linear parts.

Solution

The problem asks to express the absolute value function f(x)=3x+4f(x) = |3x + 4| as a piecewise-defined function with linear parts.

To break down an absolute value function into a piecewise function, we consider the two cases based on when the expression inside the absolute value is positive or negative.

Step 1: Set up the critical point

The absolute value function changes at the point where the expression inside the absolute value equals zero: 3x+4=0x=433x + 4 = 0 \quad \Rightarrow \quad x = -\frac{4}{3} This critical point divides the function into two intervals:

  1. When x43x \geq -\frac{4}{3}, the expression inside the absolute value is non-negative, so 3x+4=3x+4|3x + 4| = 3x + 4.
  2. When x<43x < -\frac{4}{3}, the expression inside the absolute value is negative, so 3x+4=(3x+4)=3x4|3x + 4| = -(3x + 4) = -3x - 4.

Step 2: Write the piecewise function

Thus, the piecewise-defined function is:

\begin{cases} -3x - 4 & \text{if } x < -\frac{4}{3}, \\ 3x + 4 & \text{if } x \geq -\frac{4}{3}. \end{cases}$$ This is the piecewise form of the absolute value function. Would you like more details or have any questions? --- Here are 5 questions to expand your understanding: 1. What does the absolute value represent geometrically on a graph? 2. How do we determine the critical point for an absolute value function? 3. Why does the piecewise function have two different expressions for different values of $$x$$? 4. How would you graph the piecewise function to see the transition at $$x = -\frac{4}{3}$$? 5. Can we generalize this process to any linear absolute value function? **Tip:** When working with absolute value functions, always focus on the point where the expression inside the absolute value equals zero to identify where the function changes behavior.

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Math Problem Analysis

Mathematical Concepts

Algebra
Piecewise Functions
Absolute Value

Formulas

Absolute value: |a| = a if a >= 0, |a| = -a if a < 0
Piecewise function structure: f(x) = {expression1 if condition1, expression2 if condition2}

Theorems

Definition of absolute value

Suitable Grade Level

Grades 9-12